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Full text of "Distribution and abundance of Haliotis kamtschatkana in relation to habitat, competitors and predators in the Broken Group Islands, Pacific Rim National Park reserve of Canada"

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\3 Biodiversity 

Journal of shellfish research. 

[S.I. :National Shellfisheries Association, 1981- 

v. 22 (2003): 
Page(s): Page 831 , Page 832, Page 833, Page 834, Page 835, Page 836, Page 837, Page 838 

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Jourml 0f Shellfish Research, Vol. 22. No. 3, 8JI-83&, 2003. 




1 Parks Canada, Western Canada Service Centre, 300-300 West Georgia Sneer Vancouver, BC. Canada 
Y6B 684; 2 Parks Canada. Pacific Rim National Park Reserve. Box 280 Uduelet BC> Canada VOR 3A0 

ABSTRACT Byline in Format ion on the distribution and abundance t>f Haliotis kamischatkema was obtained throughout the Broken 
Group Islands iBGl) in shallow- (2-5 ml and deep-water (6-^ m) habitats. The study demonstrates that abundance of northern {pinto) 
akilone varied spatially throughout the area and with depth. The shallow habitats in the study area supported significantly higher 
densities (048 abalpne/m 2 ± 0,02 SE) of northern abalcme when compared with deep habitats i<). H> afcilcmc/m 2 ± 0.02 SE). Maximum 
and minimum sizes of northern abalone measured in BGI were 132 and 4 nun shell length (SL), respectively. There were signifieanl 
differences in abalone SL among the 5 island groups and the 2 depth /ones. Juvenile abalones were more abundant in the deep habitat 
than in the shallow habitat. A significant correlation was detected between abalone densities and the relative index or exposure. There 
was a positive correlation between abalone size and the abundance pf benthic maeroalgae and an inverse relationship between abalone 
si/e and the abundance o| red sea urchins iStrottfiytofentrorus fniticiscanus). A positive correlation between abalone and red sea urchin 
densities was observed. Seven percent of juvenile abalone 1^4? mm SL) was found under the red sea urchins* spine canopy. 
Distribution and abundance of selected uivertebrate species associated with northern abalone including! its known predators lie. sea 
stars, crabs, octopuses) were assessed. The abundance of northern abalone was inversely correlated with predator abundance and 
density of benthic maeroakae. Detailed surveys of associated organisms and substrate types suggest that the distribution and abundance 
of northern abalone is a complex function of community interactions and substrate habitat characteristics. 

KEY WORDS: Northern (Pinto) abalone. Hut tot h kamtschafhma, red sea urchins, competitors* predators, habitat, distribution 

INTROM rnn\ 

Large, mobile invertebrates, such as abalone and sea urchins, 
are an important component on subtidal rocky reefs in the coastal 
waters of British Columbia, The northern lor pinto) abalone [Huii- 
otis hamtschalkana Jonas, 1K4.S) is found distributed from Alaska 
(Paul & Paul 1981 ) to California (Sloan & Breen 198K) along the 
west const of North America, Historically, H. fcamtsckatkana was 
widely distributed in British Columbia with preference to semi- 
exposed to exposed coastal habitats where they graze mainly on 
attached or drift maeroalgae and diatoms. Abalone are slow grow- 
ing and long-lived gastropods, characterized by patchy distribu- 
tion, sporadic recruitment, density dependent reproduction and 
short larval period (Hobday et al. 200 U They are dioecious broad- 
cast s pawners with peak reproductive activity during the summer 
(Breen & Adkins 1980). During spawning events abalone aggre- 
gate in shallow subtidal areas to maximize fertilization success, 
which depends on their aggregation density {Babcock &. Kccsing 
1499). ft is now recognized that northern abalone is particularly 
vulnerable to overexploitation because of this life history strategy. 

The coastal First Nations of British Columbia have a long 
history of harvesting northern abalone for a wide range of uses, 
tanging from subsistence harvests to use in native art and cultural 
activities (Stewart 1977). The first record of modem commercial 
abalone fishery in British Columbia dales to the early 1900s (Sloan 
& Breen 1988). Prior to the invention of SCUBA, the abalone 
fishery targeted mainly the miertidal populations; thus subtidal 
areas were in effect natural refugia. The use of SCUBA to harvest 
abalone started in the 1950s, but was generally restricted to few 
operators. Abalone commercial landings in British Columbia 
peaked in 1977 to 1978 (428-433 tons, respectively) and then 
continued to decline. Northern abalone was targeted by recre- 
ational and commercial dive fisheries until 1990. when the fishery 
was closed due to major slock declines (Campbell el al. 2000). The 
purpose of the 1990 commercial fishery closure in British Colum- 
bia was to allow the abalone populations to rebuild. However, 

numerous stock assessment surveys by Department of Fisheries 
and Oceans Canada {DFO) during the 1990s have shown no evi- 
dence of recovery (Campbell 2000). As a result, //. kamtschatkana 
was designated as threatened in 1999 by the Committee on the 
Status of Endangered Wildlife in Canada (COSEW1C). Recovery 
strategy and action plans are now in place to assist in rebuilding 
the northern abalone population to sustainable levels. This study is 
part of that strategy. 

The present study was conducted in the Broken Group Islands 
(BGlL which are part of ihc Pacific Rim National Park Reserve of 
Canada (PRNPR). A recent DFO surve\ of abalone populations in 
southeast Barkley Sound, adjacent Lo BGI. provided no evidence 
of recovery of abalone populations since the province- wide closure 
in 1990 {Lucas el al. 2002). The mean reported density of 0.1 
abalone/nr is significantly lower than the mean density of 52 
abalone/nr reported by Emmctt and Jamieson (1988) from the 
same area prior to the 1990 closure. The objective of the present 
Study is to provide baseline information for the managers of 
PRNPR on the distribution and abundance of northern abalone 
throughout the BGI at two depth zones i shallow: 2-5 in below 
chart datum; and deep: 6-9 m below chart datum). The study was 
designed to explore the association of abalone with other compo- 
nents of their subtidal habitats, by providing key information on 
the distribution and abundance of organisms associated with the 
species, including its major known predators. The study forms the 
baseline against which to compare future response of abalone 
populations to sea oner {Enhxdnt tttiris Linnaeus. 175K), recolo- 
ni/ation of BGI. and to the expected increase m climate variability 
associated with climate change. 


Description of Study Sites 

[he BGI Archipelago is located on the Pacific coast of Van- 
couver Island in Barkley Sound, roughly between latitudes 




4ti -'•57.683'N and 48 ■■"50. 233 'N, and longitudes 125°12.700'W and 
125°24.700'W (Fig, h. Based on geographic and oeeanographic 
features, the BGI were sub-divided into 5 island groups and strati- 
fied in two depths. The 5 island groups were: Group I. Hand: 
Group 2 T Dodd: Group % Clark; Group 4, Wouwer; and Group 5. 
Gibraltar (see Fig, I ). The tidal range within the BGI is approxi- 
mately 3.8 m. Based on past studies by DFO, each of these island- 
groups was stratified into shallow (2^-5 m below chart datum) and 
deep (6-9 m below chart datum) /ones reflecting the distribution 
of northern abalone populations (eg, McShane & Naylor 1995, 
Sloan & Breen 1988, Campbell et al. 1998, Campbell el al 2000, 
Lucas et al. 2002). 


A 200 x 200 m geo-refcrenced grid was laid over each of the 
5 island groups using AnGIS 8.x software. All 200 x 200 m blocks 

that intersected a shoreline or offshore reefs within each island 
group were sequentially numbered. The number of blocks that 
intersected a shoreline or an offshore reef ranged from 58 in Group 
3 to 295 in Group 5. Random selection without replacement was 
used to select 4 sampling locations tic. blocks) in Group 1. 5 
locations in Group 2. 4 locations in Group 3, 4 locations in Group 
4. and 5 locations in Group 5, for a total of 22 sampling locations 
{see Fig. I '). A relative index of exposure was computed for each 
site following procedures described by Ekebom et al. (2002). At 
each location. 2 sites approximate!} 30 m apart were sampled. 
Sampling was conducted by 2 dive teams. 

Sampling al each site was conducted by randomly placing I nr 
quadrats along 25 m virtual transects that were laid randomly 
parallel to the depth contour, Two transects were sampled within 
each depth zone at each site. The position of transects within each 
depth zone was determined by randomly selecting two specific 

Group 4 


12 3 


Hgure L Map of" the Broken Group Islands within the Pacific Rim Nalmnul Park Reserve located on the west coast of Vancouver Island. British 
Columbia. Canada. Dark lines represent the rough boundaries of the 5 groups in which randomly chosen slud> locations were set up + Black dots 
and associated numbers Indicate ihe nuniher and position of each stud> location in the survey. The S geographic groups were: Group 1, Hand: 
Group 2, Dodd; Group 3, Clark; Group 4, Wouwer; and Group 5, Gibraltar. 

Distribution and Abundance of H kamtscnatkana 


depths within each zone (shallow /one; 2, 3, 4, and 5 m; deep /one: 
6, 7, 8 T and 9 m). Ten random 1 m 2 quadrats were sampled along 
each 25 in virtual transect. The positions of the 10 random quadrats 
along each transect were determined by randomly selecting 10 
numbers between ] and 25. The random quadrat selection was 
conducted prior to the survey and marked on underwater recording 
sheets thai were specific for each sampling transect. The starting 
point of each transect was selected haphazardly b> swimming 
along the deplh contour and dropping die quadrat after about a 1 to 
2 min swim. Once the starting point was determined the divers 
proceeded to flip the I nr quadrat along the virtual transect until 
I hey reached the first predetermined randomly selected position 
Quadrat sampling included divers carefully filling up (hut not re- 
moving) all large maerophytes from the quadrat area to facilitate 
the systematic search for both emergent and cryptic specimens. 
Rocks were not removed or turned over in this survey. Once sam- 
pling of the quadrai was completed divers proceeded to Hip the 
quadrat to the next randomly selected position along the virtual 
transect. This procedure was repealed until [ill 10 quadrats were 
sampled, or divers were forced to surface due to safely consider- 

Ah alone and red sea urchin {Strongylocentrotus fremciscanus 
Agassiz, 1863} counts, including maximum shell length (SL) and 
test diameter (TD) measurements in mm. were recorded in all 10 
qii.tdm^ in each iraiiscci The green sea urchin, Strmgtfl^entF&tjts 
droebmhiensh (OF. Midler, 1776) and the purple sea urchin, 
Strongyiocentrotus purpuratus (Slimpson, 1857) were also re- 
corded. The number and si/c of juvenile aba I one found under the 
red sea urchin spine canopy were also recorded in each quadrat. 
Predator densities, including dungeness crab (Cancer magister 
Dana, 1852), red rock crab (Cancer prdductits Run da IK IS39), 
octopus {Enierottopus doflewi Wiilker, 1910), and sunflower sea 
star {Pycnopodia keltanthoides (Brandt, L835)), were recorded in 
all quadrats along each transect. For octopuses, either individuals 
or inhabited dens were counted. Sea otters were not observed in the 
study area 

Densities of benthic macroalgae were estimated in 5 randomly 
selected 1-nr quadrats (from the anginal 10 quadrats) along each 
transect. Because of time constraint, ease of taxonomic identifica- 
tion and reporting efficiency, ihe following macroalgae were in- 
cluded: (1) Microcystis int&grifplia Bory. 1826; (2) Nereocystis 
luetkeana (Mertens) Postels et RupreehL 1840; (3) Fucus spp.; (4) 
Eisenia arborea Areschoug. 1876: (5) Hedopliylhtm sessile (C. 
Agardh) Seichell, 1901; (6) Ag&futh clathratum Dumortier, 1822; 
(7) Pterygophora California! (Ruprecht, 1852); (8) other browns; 
and (9) green algae. In each quadrat, the macroalgae were iden ti- 
lled and counted. Algal holdfasts were counted for all species 
except M. integrifolia for which the number of stipes was used. 

The following substrate cover types were defined in the present 
study: El ) encrusting coralline algae, (2) articulated coralline algae, 
(3) brown algae, (4) green algae, (5) bryo/oans, (6) sponges, {7) 
other invertebrates, and (8) sand. The percentage cover of each 
substrate type was quantified in 3 randomly selected I m~ quadrats 
(from the original 10 quadrats) in each transect using a point- 
intersect method. This method involved the use of a quadraL which 
was permanently marked along one side with 20 points (5 cm 
apart), and a 1 m PVC bar that was permanently marked with 5 
random points. Sampling involved placing the 1 m PVC bar across 
ihe quadrat from 3 randomly chosen points along the side of the 
quadrat and recording the substrate type that was found under each 
of the 5 points on the PVC bar. The three random points along the 

side ol the quadrat were chosen earlier and were marked on re- 
cording sheets. Each quadrat was sampled with 15 points i45 
points per transect). 


All data analyses were conducted using the NCSS statistical 
package (Hintze 2001). Tests of mutuality and homogeneity of 
variance were performed on all data sets using normal probability 
plots and modified Levene equal variance test, respectively. 
Square root (SQRT) and ARCS1NE(SQRT<X» transformations 
were performed as appropriate fZar 1996) and the assumptions 
were tested again on the transformed data sets to verify the success 
of the transformations. 

A nonparametrie Kruskai-WalSis one- way ANOVA on ranks 
was used to compare abalone and red sea urchin densities, as well 
as red sea urchin test diameters, among the island groups and depth 
/\ mes, since ni> transformation was able to normalize the data. This 
non-parametric procedure tests the null hypothesis that all medians 
are equal and is an accepted substitute for one-way ANOVA. 
Where significant \F < 0.05) aiming group ditterences were indi- 
cated* we used the Kruskal-Wallis multiple-comparison Z-value 
lest to find specific among group differences. The Z- values are 
appropriate for testing whether the medians of any two groups are 
significantly different. 

One-way ANOVA (fixed model) was used to compare abalone 
shell lengths uiniiansformed) among the 5 island groups and be- 
tween the two depth /ones. To identify specific among group 
difference we used the Tukey-Kramer multiple-comparison test, 
which examines all pairs of group means. The Kolmogorov- 
Smirnov goodness of fit km was used io compare abalone and red 
sea urchin size frequency distributions between the shallow and 
deep /ones. The nonparametrie Spearman Rank Correlation was 
used to assess the relationship between the relative exposure index 
and abalone densities, since transformations failed to normalize the 
data. The test produces a correlation coefficient (rj. which may 
range from -1 to 1* and it has no units (Zar 1996). The parametric 
Pearson Product-moment Correlation analysis was used to identify 
significant relationships between the abundance of northern aba- 
lone (SQRT transformed) and the various substrate cover types 
(ARCSINE(SQRTcX) transformed). This procedure was also used 
to examine relationships among abalone. red sea urchin, predator, 
and macroalgae densities (SQRT transformed). The test produces 
a simple correlation coefficient (r), which is unitless and ranges 
from -1 to 1. Simple linear regression analyses were used to assess 
the relationships between abalone size (untrans formed l. red sea 
urchin densities (SQRT transformed), and benthic macroalgae den- 
sities luntransformedi. One location (group L location 2} was 
excluded from these regression analyses because no abalone were 
found at this location. 


Distribtitifttt and Abundance of Abalone 

Northern abalone were present at all island groups surveyed in 
this study, although in varying densities (Table 1 ). The result of the 
Kruskal-Wallis one-way ANOVA on ranks indicated significant 
differences (P < 05) in abalone densities among the 5 island 
groups. The Kruskal-Wallis multiple-comparison Z- value test re- 
vealed that abalone densities in Group 3 were significantly higher 
(P < 0.05) than at all other groups. There were no significant 


Tom asci k and Holmes 


Northern abalone, red sea urchin, predator and macroalgat densities (mean ± SE\ at the 5 Island groups and 2 depth /ones in the study. 
The numbers in parentheses are sample size - n lie, number of quadrats), n fur red sea urchins u\k\ predators is same as For ahalone. 


Group t 


Group 2 


Group 3 


Group 4 


Group 5 






0.143 ±0.03 
0. 16? ±0,0? 
0.131 ±0.03 
0.165 ±0.03 
0.044 ± 0.03 
0.266 ± 0,04 
0.288 ±0.06 

0.240 ±0.05 
0J 04 ±0.02 
0.085 ± 0.02 
0.1 35 ±0.03 
0.025 ±0.01 
I). 1 47 ±0.01 
1)4 80 ±0.02 
0.100 + 0.02 





( 1 50) 
(130 1 

Red Sea It chin 



0.596 + 0.06 
0700 ± 0. 1 2 
0.458 ±0.1 JK 
0,456 ±0.07 
0.370 ± 0,07 
0.678 ±M7 
2.538 ±04 3 
3,059 ±0 IV 
1.947 ±0.16 
1.242 ±0.12 
0,915 ±0 14 
1.627 ±0.20 
0.244 ± 0.06 
0.264 + lu 

0,219 ±0.06 
0-997 ±0.05 

1.005 ±0.07 
0,987 ± 0.07 

(Number/m 2 ) 

0.200 ± 0.03 
0,225 ± 0.04 
0,167 + 0.04 
0.228 + 003 
0.261 +0.03 
C 144 ±0.04 
0.166 ±0.03 
0.141 ±0.03 
0.193 ±0.04 
0,208 ± 0.04 
0.208 + 0.05 
0,209 ±0.05 
0,241 ±0.03 
0.306 ±0.04 
0.163 ±0.04 
(1210 ±0,01 
0.233 ±0.02 
0.176 ±002 

I Number /m "l 

0.943 ± 
0.725 ± 
1.233 + 
4.176 + 
5.042 ± 
1 .867 ± 
2.565 + 
3.07] ± 
1.927 ± 
4.486 ± 
4.367 ± 
4.627 + 
2.534 + 
2.883 ± 
2.038 ± 

0.21 (80) 
0.29 (60> 

0.51 (45) 
0.43 1124) 

42 (181J 

0.55 (98) 



differences in abalone abundance among the other 4 groups (P > 
0.05). Mean abalone densities in the shallow /tine (0.18 ± 0.02 SB) 
were almost twice as high than in the deep /one (0.10 ± 0.02 SE). 
The Kruskal-Wallis Z-value test revealed significant differences 
iP < 0.05) in noithern abalone densities between die shallow and 
deep zones. 

The mean SL of H, kamtschatkana measured in this study was 
59.4 mm l± 2,0 SE: n = 222). The results of one-way ANOVA 
revealed significant differences in the mean SL of northern aba- 
lone among the 5 island groups. The mean SL of abalone in Group 
3 was significantly smaller (P < 0.05) than those of Groups 2, 4, 
jin[ 5 i Table 2 and Table 3). Largest abalone were found in Group 
2 followed by Group 4. No differences [P > 0.05) in abalone size 
were found between groups I Sc 3, I & 4, 2 & 5. and 4 & 5. The 
area with the highest densities pf abalone (i.e., Group 3) was also 
the area with the smallest abalone. In general, the mean SL of 
abalone in the shallow depth zone (0 = 64.7 mm ± 2,4 SE) was 
significantly larger than in ihe deep-water habitat (0 = 46,3 mm 
± 3.2 SE) (one-way ANOVA; F = 18.1: P < 0.001 ), The results 
of the Kolmogurov-Smirnov test indicated that differences in aba- 
lone size frequency distributions between the shallow and deep 
zones were statistically significant (P < 0.001 ) (Fig 2l 

Distribution and Abundance ttf Red Sen { rchins 

The red sea urchin (S, fraruiscamts) was the must abundant 
eehinoid in the study area. The abundance of both green (.S\ droe- 
bachiensis) and purple (5 purpuratus) sea urchins was so low (i.e., 
17 and 5 individuals, respectively! that they were left out of the 
analysis. Red sea urchins were found in all island groups (Table I ). 
Significantly higher mean red sea urehin densities (urehins/m 2 ) 
were found in Group 3 than anywhere else in the study area (Table 
4). No significant differences in red urchin densities were observed 
between groups 1 & 2 and groups 2 & 5, For all areas combined* 
red sea urchin mean densities were not different between the shal- 
low-water zone (1,01 ± 0,07 SE % n = 833) and the deep-water zone 

(0.09 ± 0.07 SE, n = 630) (Kruskal-Wallis Z-test; : = 1.936; P 

The results of the Kruskal-Wallis Z- value test revealed signifi- 
cant differences {P < 0.05 ) in red sea urchin TD among the 5 island 
groups (see Table 2; Table 5). The mean TD of red sea urchins in 
Group 3 was significantly smaller (80.4 mm ± 1 .0 SE) when com 
pared with cither groups, with the exception of Group 5, Red sea 
urchins in Group 4 had largest mean TD (91.3 mm ±11 SE). No 


Summan slulisties imean ± SE) lor masurium shell length (mm ) (if 

northern abalone and maximum test diameter Emm) nf red sea 

urchin at the 5 island groups and 2 depth /ones in the study. 

Sample size lie, number of individuals measured) in parentheses. 



Red Sea Urchin 


Shell Length (mm) 

Test Diameter (mm) 

Group J 

51.2 ±4.3 (38) 

87.5 ±4.0(136) 


57.5 ±6.1 (24) 

82.0 ±5.5 (82) 


40.4 ±3,6 114) 

95.8 ± 5.3 1 54 1 

Group 2 

83.0 ±4,7 142) 

88,9 ±2.7 (143) 


84.7 ±4,6 (38) 

924 ± 3.4 1 84) 


66.3 ±23,5 (4) 

83.9 ±4.3 (59) 

Group 3 

46.1 ±2.5(87) 

80,4 ± 1.0(811) 


49,9 ±3.2 (501 

82.8 ± 1.2(517) 


41,0 ±3.8 (37) 

76.0 ± 1.5(294) 

Group 4 

62.7 ±6,1 (25) 

91.3 ± 1.1 (301) 


613 ± 7.0 i 20} 

91:8 ± 1,6(179) 


68,4 ± 13,4(5) 

90,4± 1.4(122) 

Group 5 

72.4 ± 4.4 1 30) 

83.6 ±6.0 (75) 


73,0 ±4.9 (26) 

96.0 ±8,5 (35) 


68.5 ± 10,0(4) 

72.8 ±8.3 (40) 


59.4 ±2.0 {222) 

84-2 ±0.8 (1466) 


64.7 ± 2.4 (158) 

84.3 ± 1.1 (845) 


46.3 ±3,2 (64) 

84 1 ± 1.2(621) 

Distribution and Abundance of /f kamtschatkana 


l'\w i V 

Results of one-wav ANO\ A and the Tukcv-kramer 

multiple-comparison lest to discern statistical^ significant 

differences in tin- shell !i nii,lh (mini of northern ;il>,jluin .nn<ni- ilu 

5 island groups irk ilu* slud>. (iroup designation as in Figure I. 



Sum of 

Mean Proh 

Square K- Kill in Level 

A: Grtmp 



1 1 634 J 9 





Total (Adjusted) 


195360 2 



16.% 0.0O0* 

* Term significant ill alpha = 0.05 

Tu ke v Kramer Multiple Comparison Test 









Represents signifieanl difference at least at P < (105 level NS indicates mi 
significant difference heivveen groups. This report provides multiple com- 
parison tests for all pairwise differences between the means. 

relative index of exposure was not correlated with macroalgae 
densities and other substrate cover types. Encrusting coralline al- 
gae were a dominant substrate cover type in all groups, ranging 
liom 50% to 867r (Table ft). In Groups I, 3, and 5 encrusting 
coralline algae occupied more than liYk of the available substrate. 
The highesi percent cover by encrusting coralline algae was mea- 
sured in Group 3, where they covered 85,9% of the substrate. The 
percent cover of eric rust inti coralline algae in CJroup 3 was sig- 
nificantly higher that in any other group (Kruskal-Wallis multiple 
comparison Z- value test; P < 0.05). Articulated coralline algae 
represented relatively low percentage of substrate throughout the 
study area, ranging between 7M to tVv 

1 r [ t } r p 1 1 r r 1 1 1 f 

20 40 60 80 100 120 140 

significant differences in the TD of red urchins were found be- 
tween groups 1 & 2. I Si 4. I & 5, 2 Si 4, and 3 & 5\ There were 
no differences in red sea urchin TD between die two depth /ones 
(Kruskal-Wallis Z-test: z = 0,443; P > 0.05}. The size frequency 
distribution of red sea urchins in RGI for both depth zones were 
combined (Fig. 3X since the Kolmogorov-Smirnov goodness of fit 
test indicated no differences (Dtnn = (I. On, P > 0.05) in size 
frequency distribution between the two depth zones. 

/ fit hi kit Hi iatio tish ips 

The relative index of exposure was positively correlated with 
ahaloue densities (j 1X61., P ■ 0*003; n 22), red sea urchin 

densities [r s = 0.54, P < 0.01: it = 22) and with encrusting 
coralline algae ir s = 0.44, P < 0.05; ir = 22), but was inversely 
related to predator abundance {t\ = -0.45; P < 0.05; n = 22). The 


kruskal-Wullis multiple comparisons Z- value test to discern 

statistical!} significant differences of red sea urchin (S. 

fram-hcttnitsK densities (# individuals/m : l amori^ 5 island groups. 

Numbers represent Z-values lor the Kontermni Tesl iHiiitze, 20011. 

Bold numbers indicate significant differences among groups at P < 

0.05. (iroup designation as in Figure 1. 



















IS. 67 


Bonferroni Test: Medians significantly {P < 0.05) different if Z- value > 
2.8 I 



20 40 60 80 10C 120 140 





.iihii.1 . 

i 1 — t — i p — i 1 1 1 1 ■ r 


20 40 60 80 100 120 140 

Figure 2, Size frequency distributions oi' northern nhaloiic (//. ku- 
misrhtitktunn I mm IM, 1 measured during the stud>. (A) All ahalone 
measured daring the sludv in litil at both thallnu and deep /ones, i\\\ 
ahalonc measured in shallow /oni^, {V) ahalonc measured in deep 
/nnes. The si/e frequency distributions at the shallow (Bl and deep (G) 
/.ones were significantly different < Kolmogorov— Smirnnv goodness of 
111 test Dmti = 0.32; P < 0.001 ]. The vertical axes represent nam her of 
a ha I one per si/e class. 




Kruskal-W nil is multiple torn pari sons Z- value test to discern 

statistically significant diiterenees in ihe test diameter (mint of red 

sea urchin (.$. franeisatttttxt among 5 island groups. Numbers 

represent Z 


tor Ihe Bonferroni 

Test lHintaM.\ 200 1>. Bold 



indicate si^mlK 

mil differences 

am ring groups at /* < 0,(15, 


Group cJ 

esiginitinn as in Figure 1. 




3 4 5 











5.75 — 



0.25 3.24 — 

Bonferroni Test: Medians significantly different if /-value > 2.8070 

Com m Ktt ity Relation s it ips 

The results of simple linear correlation analysis revealed a sig- 
nificant positive relationship between abalone and red sea urchin 
densities (r = 0.48. P < 0.05; n = 22). A significant inverse 
relationship was found between abalone and predator densities ir 
- -061; P < 0.01: n = 20), as well as between abalone and 
bentbie maeroalgae densities (r = -0.43: P < 0.05; H = 22), A 
significant negative correlation was also found between red sea 
urchin and benthic macroalyae densities (r - -0 60: P < 0.001 ; u 
= 22). While encrusting coralline algae showed a strong positive 
correlation with red sea urchin densities (r - 0,75; P < 0.001 ; n = 
22), they showed no correlation with abalone densities \P > 0.05 I. 
The results of simple linear regression analysis revealed a signifi- 
cant inverse relationship between abalone size and red sea urchin 
densities (r = 33, P < 0.001; ti = 21). Furthermore, simple 
linear regression found a significant positive relationship between 
abalone size and abundance of benthic niacroakae {r 2 = .54, P 
< 0.001: n = 21). 


The results of this study concur with recent surveys by DFO 
(Lucas et al. 2002). The estimated mean density of abalone in this 
study (0J5tar) is similar to the mean abalone density fOJO/nr) 





T — i — i — I — l — I — i — i — i — r~n — i — i — i — r — i — n — i 

30 60 90 120 150 180 

Figure 3. Size frequency distribution of red sea urchins iS.frttticisca- 
nusi from lUil measured during the sfud), Test diameter frequencies 
from shallow and ch ep /.ones were combined. The vertical a\is repre- 
sents number of red sea urchins per size class. 

reported by Lucas et al, (2002) from an adjacent area only a few 
kilometers away. These values are in sharp contrast to mean den- 
sity values reported from the north coast of British Columbia be- 
i ween ISI78 and 1 984 (0.65 to 2.86 abalone/nr, Sloan & Breen 
IS)HiS). Surveys conducted in the Queen Charlotte Islands in 1978 
reported densities of up to 28 abalone/nr (Breen & Adkins 1979). 
The si/e range of abalone in Barkley Sound changed from 51 to 
140 mm SL in 1964 (Qnayle 1971 ) to 38 to 119 mm SL in 2000 
(Lucas et al. 2002). The size range recorded in this study was 4 to 
132 mm SL. with a mean of 59,4 mm SL Roughly 109* of the 
abalone population measured in this study was more than 100 mm 
.SL, while 58% of tbe sampled abalone population was more than 
SO mm SL (Fig. 2A). Although northern abalone reach sexual 
maturity between 50 to 55 mm SL (Sloan & Breen 19SS), juvenile 
abalone represented 42% of the sampled population. This sug- 
gested that abalone recruitment was occurring, albeit at relatively 
low numbers* 

The low densities of abalone, as well as low abundance of large 
si/e individuals recorded in this study may be related to several 

I . i -u up 



Summary statistics fur percentage cover or eighl (8) substrate cover types measured during the study. 


















4 4 







5 2 








Substrate Types 





II (i 













{±0,1 ) 





9. El 





I s 








o I 























First number is the mean % cover; second number in brackets is + standard error iSE)> Acronyms: EC encrusting coralline algae: AC. articulated coralline 
algae; BA. brown macroaigse; GA + green macppalgae; BR, bryozoans; S, sand; SP, sponges (Porifera); O, oiher invertebrates. «, sample size (# ot 
quadrats). Island Group designation as shown in Figure 1. 

Distribution and Abundance of H. kamtschatkana 


factors, such as human exploitation tie,, poaching), competition, 
predation, starvation, disease, differential mortality, or environ- 
mental factors, Ocean-climate variability may also play a role in 
keeping abalone populations at their current low levels, Tegner et 
al. (2001) demonstrated a strong link between declines in landing 
of red abalone {Haliotis nifescens Swain son, 1822) in southern 
California and increased variability in sea surface temperatures 
(SSTs) associated with HI Nino events thai affect kelp abundance, 
However, the inverse relationship between abalone and predator 
densities found in this study suggests that predation may be an 
important factor contributing to preseni day structure of abalone 
populations. The low abundance of large abalone (>l 10 mm SL) 
suggests that large abalone ma\ he more susceptible to predation 
than small individuals (<7f) mm SLi. Predator^ ma\ be preferen- 
tially selecting larger individuals, or as abalone reach larger size 
they may loose the ability to either outrun or hide from the preda- 
tors. In contrast, Watson (2000), citing Sloan & Breen (1988), 
suggested that only sea otters and human exploitation seem to have 
a significant impact on the abundance and size of abalone popu- 

There was a significant positive correlation between abalone 
and red sea urchin densities This is in contrast to studies con- 
ducted in California, where consistent negative correlations be- 
tween H. nifescens and red sea urchins were found, suggesting 
spatial inter-specific exclusion between these two species (Karpov 
et al, 2001), The red sea urchin is viewed as perhaps abalone' s 
most important competitor for space and food, since both species 
are grazers competing for the same food resource and space. The 
positive relationship therefore suggests that competition for food 
and space may not be direct, and that abalone may be in some way 
benefiting from their association with the red sea urchin. The 
positive relationship between abalone and red sea urchins in this 
study may be partly a function of lower population densities than 
those reported previously. For example, Watson (1993) reported 
that mean red sea urchin densities in Barkley Sound between 1988 
to 1989 were about 6,9 urchins/nr, which is about 7 fold higher 
than at present, Current abalone densities in the BG1 are about 4 
times lower that pre-closure (Ertimett & Jamieson 1988), At these 
low densities direct competition between abalone and red sea ur- 
chins may not be apparent. However, we also found a significant 
negative correlation between abalone size and red sea urchin abun- 
dance. This negative relationship suggests that the urchins may be 
exerting some degree of influence on abalone populations through 
their effect on either encrusting coralline algae or bent hie mao 
roalgae. Densities of both species exhibited a significant negative 
correlation with macroalgae abundance. Although abalone si/e 
also showed a strong positive relationship w ith benthic algal abun- 
dance, food availability may have played a key role in this inter- 

The significant positive relationship between red urchins and 
encrusting coralline algae and the negative relationship with 
benthic macrophyles suggests that the presence of sea urchins may 

in Mime way benefit abalone through their maintenance of a habitat 
that is preferred by juvenile abalone. Sloan & Breen (1988) sug- 
gested that abalone sell lenient occurs on eiiCriJStillfi corallines in 
deeper water and that juveniles and adults migrate upwards as ihey 
grow: Sasaki & Shepherd (2001) showed that e/o abalone i Hali- 
otis discus harmai I no, 1952) settled on encrusting coralline algae 
and moved into shallow Eisenia forest as they aged. Several other 
studies have also suggested that abalone prefer to settle on sub- 
strates dominated by encrusting coralline algae (Shepherd & 
Turner ls>8\ McShune 1995). However, the primary food source 
lor abalone, essential for rapid growth of post-larval abalone, may 
be the associated diatoms rather than the encrusting coralline algae 
themselves (Takami et al. 1997). Encrusting corallines were found 
to occupy about 71$ of the substrate in the deep zone (6-9 m). 
which was statistically higher than the 66% cover in the shallow 
zone (2-5 m). 

Vance ( 1 979) suggested that echinoids play a key role in struc- 
turing algal turf communities by removing encrusting inverte- 
hraiev thus promoting the growth of encrusting coralline algae. 
This study found a strong negative correlation between encrusiing 
coralline algae and "other invertebrates". By maintaining encrust- 
ing coralline algae free of other invertebrates, the red sea urchin 
may indirectly influence abalone settlement rates and perhaps post 
settlement survivorship. However, the present study supports ear- 
lier studies in British Columbia thai round no significant associa- 
lion of juvenile abalone with red sea urchin spine canopy (Sloan & 
Breen 1988), even though there was a positive correlation in the 
densities of these two species. In contrast several recent studies 
around the world have shown that juveniles of some Haliotis spe- 
cies have a strong, association w iih the sea urchin spine canopy (eg, 
Day & Branch 2002). We found only six juvenile abalones (^45 
mm SL) under the red sea urchin spine canopy, which represents 
only 1% of all juvenile abalones recorded in this study. Rogers- 
Bennett &: Pearse (2001) reported that one third ol" juvenile aba- 
Lone inside a marine protected area was found under the spine 
canopy of sea urchins. 


The authors thank Rick Holmes, Pete Clarkson, Bob Hansen, 
Sebastian Marcoux, and Angus Simpson (Pacific Rim National 
Park Reserve of Canada, PRNPR). as well as. Doug Brouwer and 
James Pegg (Pacific Biologic Station [PBS], Nanaimo, DFO) for 
conducting abalone surveys and field support. Joanne Lessard and 
Ian Murfitt (PBS) for computing the index of exposure, and Greg 
Mac Mil Ian and Steve Lobay (Western Canada Service Centre, 
Parks Canada) for their technical support The authors thank Alan 
Campbell (PBS) and Larry Harbidge (Chief of Resource Conser- 
vation PRNPR) for their continuous support in this interdepart- 
mental research project. This manuscript was greatly improved by 
comments from ihree reviewers and A, Campbell This project was 
funded by the Species at Risk Interdepartmental Recovery Fund 


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